Analysis of pollen loads in a wild bee community (Hymenoptera: Apidae) — a method for elucidating habitat use and foraging distances

Abstract

Resource utilisation and foraging ranges of Apidae (excluding Apis and Bombus) were studied in sandy grasslands of the temperate zone by pollen analysis combined with direct observation of bees. Planttaxa composition of 558 pollen loads collected from 56 bee species was determined. We recorded flower-visits using plot-based observations and resource utilisation using pollen analysis. For the most important entomophilous plant species flower-visitation and pollen-analytical data correspond (e.g. Berteroa incana, Centaurea stoebe, Potentilla argentea). Whenever pollen of plant species that are limited in their occurrence could be detected, we were able to use pollen analysis to determine foraging distances, but not maximum foraging distances. Using tree pollen, minimum flight ranges up to 1250 m were documented even for bees with 7 mm body size. Thus pollen analysis not only provides valuable information about foraging on different spatial scales, but also enables foraging ranges to be calculated without experimental manipulation.